As one of the representative mobile communication standardization organizations, the 3rd Generation Partnership Project (3GPP) has developed Evolved Packet System (EPS) and defined Mobility Management Entity (MME). In order to meet the high speed mobility and reinforced security requirements of such a next generation mobile communication system, it has been proposed to improve the NAS protocol used in the conventional mobile communication systems, especially the 3G system of 3GPP.
However, the NAS protocols and mobility, location, and registration management schemes of the NAS based on the NAS protocols are not matures to provide definitions of accurate procedures and properties for supporting the aforementioned functions. Also, the currently defined procedures and messages have malfunctioned and brought out unclear problems in association with the mobility, location, and/or registration managements in the real system. There is therefore a need of the definitions on the procedures for efficiently supporting the mobility, location, and registration managements, security protection of NAS protocols, and the roles of the UE and MME.